This type of fuel cell stack has a sealing structure for preventing leakage of reactive gas and coolant to the exterior of the fuel cell stack. In the technique described in Japanese Laid-Open Patent Publication No. 2004-342493, a pair of separators is formed by pressing thin plate-like metal members. A protrusion is formed on the first separator out of the two separators through pressing to provide the sealing structure. The protrusion of the first separator is brought into contact with a flat surface of the second separator. Since the protrusion is formed by a thin plate-like metal member, the protrusion is elastic. Therefore, as described in the aforementioned document, sealing performance is obtained by applying load to the first and second separators while maintaining contact between the flat surface of the second separator and the protrusion of the first separator.
The above-described fuel cell stack is required to minimize displacement between fuel cells when the fuel cells are stacked together. If such displacement is large, components such as the separators move to an unexpected extent when load is applied to the fuel cells. This deforms gas passages and thus increases pressure loss of the reactive gas. As a result, power generation performance and sealing performance may decrease.
To restrain such displacement to an acceptable range, positioning pins may be employed in a step of stacking fuel cells together. This may complicate the equipment and operations needed in the manufacturing steps.